Executive producer: Gene Roddenberry
Associate producers: Edward K. Milkis and Gregg Peters
Producer Fred Freiberger
Co- producer: Robert H. Justman
Story consultant: Arthur H. Singer

Writer: Margaret Armen
Dir.: Jud Taylor

Captain Kirk: William Shatner
Science Officer, First Officer, Cmdr. Spock: Leonard Nimoy
Dr. Leonard "Bones" Mc Coy: DeForest Kelly
Lt. Sulu: George Takei
Lieutenant Commander Montgomery Scott: James Doohan
Lieutenant Uhura: Nichelle Nichols
Miramanee: Sabrina Scharf
Salish: Rudi Solari
Goro: Richard Hale

Stardate 4842.6

An inhabited planet is shortly before a collision with a big asteroid. To find out about the planet Kirk, Spock and McCoy beam down and find themselves in a paradise–like nature, where they watch people who look, live and behave very much like the Red Indians in ancient America. Near the village where they have seen the people they find an obelisk. It is covered with symbols that none of the three is able to decipher. The material and make indicate that it is not from the people of the village. 

The moment Kirk wants to use his communicator to get into contact with the Enterprise, a trapdoor underneath him opens and he falls down, right into a room underneath the obelisk. Spock and McCoy were some distance away and did not notice what happened. Inside the obelisk, a purple beam renders Kirk unconscious. Since they do not find the captain, but have a notion that the obelisk is involved in the vanishing of their captain, Spock takes with him all the information he can and both are forced to return to the Enterprise to destroy the asteroid. McCoy would have preferred to search longer for Jim, but Spock takes two stones and shows the distance of the asteroid to the planet and how it is diminishing. 

While Spock does not sleep but uses every spare minute to find out about the symbols of the obelisk, Kirk's memory has mostly be removed by the ray. He finds a way out just the moment the priestess, Miramanee, is close to the obelisk and she sees him coming out. She was to marry the son of the chief, but falls in love with Kirok - as Kirk is called since he cannot remember his name to the full. The crew of the Enterprise tries to break the asteroid with phaser beams. In spite of increasing the power the asteroid proves to need more than that. And the Enterprise breaks her own engines. The only possibility for the ship to go back is by speed lower than the speed of light – preceding the asteroid. This takes them 7 months until they are back to the planet. 

McCoy is worried about Spock: He has not slept or eaten since days. McCoy threatens Spock to have him safe guarded to sickbay if he won't sleep, and leaves when Spock answers by lying down on his bed, without a comment. Not a second after the doctor is out Spock gets up and back to work in search for the meaning of the symbols. Kirk is by now the acknowledged Medicine Chief of the tribe to whom they turn in critical – situations, a status like a god. He and Miramanee are married – much to the dismay of her supposed to be husband, Salish. Miramenee, is with Kirk's child. 

Through a lot of hard work, while blaming himself that they were not able to find the captain and not having succeeded in breaking the asteroid Spock has managed to decipher the readings on the obelisk: An ancient race had been the origin of the people on the planet. They also have left the obelisk which can deflect asteroids from the planet. Dangerous changes in the atmosphere frighten the people of the tribe as the obelisk comes closer. In search for help they turn to Kirok, who does not know what to do. Salish, who never liked Kirok, manipulates the frightened crowd to stone Kirok, because he is not a god. He is chased to the obelisk. 

Spock and McCoy beam down and the crowd disperses. They find the two stoned and Miramanee dying. Spock cares for her and makes McCoy bring down nurse Chapel, who does the best she can for Miramenee. Spock asks her why they were stoned and she explains to him that Kirok-Kirk was not able to bring his people into safety, to open the obelisk. Realizing that Jim has lost his memory, Spock begins a mind meld to help the captain. He almost loses himself in the meld and when he finally succeds to break it, he explains to the doctor that this was very difficult because Jim has a very strong personality. 

Kirk's memory is restored and both end the mind melt being fully aware what they are – by this indicating the end of the personality change. Kirk now remembers. He had opened his communicator and spoken. By repeating this, the entrance opens and Spock enters the obelisk. Kirk stays with Miramenee and has her beamed up on board. When Kirk comes down into the obelisk, too, Spock reactivates the system and the huge power of the obelisk avoids a collision of the asteroid with the planet. On board Miramenee dies from the stones thrown on her- and the child she is carrying dies with her.